[[RFC PATCH]] gpio: gpio-mxc: make sure gpio is input when request IRQ

[Shawn Guo]

On Wed, Jul 16, 2014 at 03:51:04PM +0200, Markus Niebel wrote:
> From: Markus Niebel <Markus.Niebel at tq-group.com>
> 
> When requesting an GPIO irq for imx Soc two things are missing:
> - there is no check, if the GPIO is already requested
> - there is no check, if the GPIO is configured as input
> 
> The first case can lead to reconfiguring the GPIO pin from third
> party while it is used as IRQ pin, second case will (eventually)
> prevent IRQ from being seen by SOC becaus the pin is driven by
> Soc
> 
> This patch tries to implement (logic taken roughly from gpio-omap)
> - basic check if gpio already requested
> - if needed requests the gpio and configures as IN.
> - if gpio is already requested it is only verified if pin is IN
> - gpio is locked as irq
> 
> Tested on a not mainlined i.MX6 based hardware with pin configured
> by bootloader as OUT HIGH and expecting a low active IRQ.
> 
> Signed-off-by: Markus Niebel <Markus.Niebel at tq-group.com>
> ---
>  drivers/gpio/gpio-mxc.c |   35 +++++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
> 
> diff --git a/drivers/gpio/gpio-mxc.c b/drivers/gpio/gpio-mxc.c
> index db83b3c..4316a38 100644
> --- a/drivers/gpio/gpio-mxc.c
> +++ b/drivers/gpio/gpio-mxc.c
> @@ -175,6 +175,31 @@ static int gpio_set_irq_type(struct irq_data *d, u32 type)
>  	u32 gpio = port->bgc.gc.base + gpio_idx;
>  	int edge;
>  	void __iomem *reg = port->base;
> +	int ret = 0;
> +
> +	if (!gpiochip_is_requested(&port->bgc.gc, gpio_idx)) {
> +		char label[32];
> +
> +		snprintf(label, 32, "gpio%u-irq", gpio);
> +		ret = gpio_request_one(gpio, GPIOF_DIR_IN, label);

I'm not sure it's correct to call gpio_request_one() from .set_irq_type
hook.  It looks like a API usage violation to me.  It should really be
called from client driver.

> +	} else {
> +		val = readl(port->base + GPIO_GDIR);
> +		if (val & BIT(gpio_idx))
> +			ret = -EINVAL;

It says that the GPIO is requested by someone, but we're not really sure
if it's the correct one, i.e. the one is requesting set_irq_type.

> +	}
> +
> +	if (ret) {
> +		dev_err(port->bgc.gc.dev, "unable to set gpio_idx %u as IN\n",
> +			gpio_idx);
> +		return ret;
> +	}

Having said that, I'm not sure any above changes is really necessary.
If any, I would say only gpiochip_is_requested() check makes some sense,
but we should just fail out if the GPIO hasn't been requested.  Nothing
more can be done in there.

> +
> +	ret = gpio_lock_as_irq(&port->bgc.gc, gpio_idx);
> +	if (ret) {
> +		dev_err(port->bgc.gc.dev, "unable to lock gpio_idx %u for IRQ\n",
> +			gpio_idx);
> +		return ret;
> +	}

This and the following changes do make sense to me.

Shawn

>  
>  	port->both_edges &= ~(1 << gpio_idx);
>  	switch (type) {
> @@ -231,6 +256,15 @@ static int gpio_set_irq_type(struct irq_data *d, u32 type)
>  	return 0;
>  }
>  
> +static void gpio_irq_shutdown(struct irq_data *d)
> +{
> +	struct irq_chip_generic *gc = irq_data_get_irq_chip_data(d);
> +	struct mxc_gpio_port *port = gc->private;
> +	u32 gpio_idx = d->hwirq;
> +
> +	gpio_unlock_as_irq(&port->bgc.gc, gpio_idx);
> +}
> +
>  static void mxc_flip_edge(struct mxc_gpio_port *port, u32 gpio)
>  {
>  	void __iomem *reg = port->base;
> @@ -353,6 +387,7 @@ static void __init mxc_gpio_init_gc(struct mxc_gpio_port *port, int irq_base)
>  	ct->chip.irq_mask = irq_gc_mask_clr_bit;
>  	ct->chip.irq_unmask = irq_gc_mask_set_bit;
>  	ct->chip.irq_set_type = gpio_set_irq_type;
> +	ct->chip.irq_shutdown = gpio_irq_shutdown;
>  	ct->chip.irq_set_wake = gpio_set_wake_irq;
>  	ct->regs.ack = GPIO_ISR;
>  	ct->regs.mask = GPIO_IMR;
> -- 
> 1.7.9.5
>